Can you provide an example of the bytecode produced? In the SQLite shell type:
.explain explain <query>; Typical output (with SQLite version 3.7.14.1): asql> .explain asql> explain update mytable set myfield=2 where myconst=7; addr opcode p1 p2 p3 p4 p5 comment ---- ------------- ---- ---- ---- ------------- -- ------------- 0 Trace 0 0 0 00 NULL 1 Goto 0 73 0 00 NULL 2 OpenEphemeral 1 26 0 08 NULL 3 VOpen 0 0 0 vtab:1F77F958:2B834C233990 00 NULL 4 Integer 1 1 0 00 NULL 5 Integer 0 2 0 00 NULL 6 VFilter 0 40 1 00 NULL 7 VColumn 0 1 4 00 sgb_dd_play_mode_text.game_no 8 Integer 7 5 0 00 NULL 9 Ne 5 39 4 collseq(BINARY) 6b NULL 10 Rowid 0 6 0 00 NULL ... retrieve unchanged fields 17 Integer 2 13 0 00 NULL ...retrieve unchanged fields 36 MakeRecord 6 26 4 00 NULL 37 NewRowid 1 5 0 00 NULL 38 Insert 1 4 5 08 NULL 39 VNext 0 7 0 00 NULL 40 Close 0 0 0 00 NULL 41 Rewind 1 71 0 00 NULL ...retrieve stored rows 69 VUpdate 0 27 32 vtab:1F77F958:2B834C233990 02 NULL 70 Next 1 42 0 00 NULL 71 Close 1 0 0 00 NULL 72 Halt 0 0 0 00 NULL 73 VBegin 0 0 0 vtab:1F77F958:2B834C233990 00 NULL 74 Goto 0 2 0 00 NULL Explanation: - xBestIndex is called while preparing the statement - (73) VBegin is called to signal the start of a transaction - (3) VOpen is called to open the table for reading (typically store a read-only file handle in your VT cursor structure) - (4..6) VFilter is called to establish the rowset fort he cursor (typically rewind your data file and retrieve the first record) - (7..9) WHERE condition is checked - (10..36) The new records contents is constructed from the VColumn return values and the results of the expressions in the SET clause - (37..38) The new record is stored in an ephemeral table - (39) VNext is called (typically retrieve the next record) - (40) VClose is called (typically close the read only file handle in your VT cursor structure) - (42..68) The new record is retreived from the ephemeral table - (69) VUpdate is called (typically open a read-write file handle and store it in your VT table structure) - (70) retrieve next row for update - (71) Close the ephemeral table (and automatically drop it) -(72) End program, calling VCommit to signal the end of the transaction (typically flush and close the read-write file handle in the table structure) Note that opening a read-write file handle is done on the first VUpdate instead of VBegin because there may be no rows that require updating. -----Ursprüngliche Nachricht----- Von: sqlite-users [mailto:sqlite-users-boun...@mailinglists.sqlite.org] Im Auftrag von Bob Friesenhahn Gesendet: Dienstag, 28. März 2017 21:49 An: SQLite mailing list <sqlite-users@mailinglists.sqlite.org> Betreff: [sqlite] VT table behavior change between 3.10 and 3.17 We are trying to update from sqlite3 3.10 to 3.17. Our virtual table modules are encountering problems with 3.17 since the 'xOpen' callback is now being called for value change and row deletion operations. Previously it was only being called for read-only queries. We are using reader/writer locks and there is not a convenient way to transition from being a reader to being a writer. A file is opened by the 'xOpen' callback and we need to know if the file should be opened read only, or read/write. The change in behavior can only work with virtual table modules which are able to smoothly transition between the state established by 'xOpen' to the 'xUpdate' call or know the intent when 'xOpen' is called. This did not seem to be a requirement before. In what sqlite3 version did this behavior change? Is there a way to know when the 'xOpen' callback is called if it is to support an update transaction (i.e. 'xUpdate' callback will be called)? Thanks, Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users ___________________________________________ Gunter Hick Software Engineer Scientific Games International GmbH FN 157284 a, HG Wien Klitschgasse 2-4, A-1130 Vienna, Austria Tel: +43 1 80100 0 E-Mail: h...@scigames.at This communication (including any attachments) is intended for the use of the intended recipient(s) only and may contain information that is confidential, privileged or legally protected. Any unauthorized use or dissemination of this communication is strictly prohibited. If you have received this communication in error, please immediately notify the sender by return e-mail message and delete all copies of the original communication. Thank you for your cooperation. _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
